What is driving Apple's fight against the FBI? Critics question motives.

As the deadline approaches for Apple to make its case against the FBI's request for assistance in cracking open an iPhone, many are lining up in support of the tech giant. But skeptics question what lies behind the legal battle.

A worker tries to repair an iPhone in a repair store in New York, February 17. Apple Inc. will likely seek to invoke the United States' protections of free speech as one of its key legal arguments in trying to block an order to help unlock the encrypted iPhone of one of the San Bernardino shooters, lawyers with expertise in the subject said this week.

The saga of Apple’s fight against a Federal Bureau of Investigation request for assistance in breaking into an iPhone continues to gather pace.

Other major tech companies are lining up to offer Apple support in its efforts to protect privacy, and myriad other people and organizations are wading into the fray with their own opinions, not all of which are quite so sympathetic with the stance of the iPhone producer.

Both Apple and the federal government appear to be digging into the history books as they search for legal precedents to defend their corners.

“The United States government has demanded that Apple take an unprecedented step which threatens the security of our customers,” wrote Apple CEO Tim Cook in a statement Tuesday. “We oppose this order, which has implications far beyond the legal case at hand.”

The FBI has filed a request that would require Apple to essentially construct a back door into the iPhone used by one of the shooters involved in the Dec. 2 terrorist rampage in San Bernadino, Calif.

While the government insists the mechanism would only be used this one time, the general concern is that, once created, it would unleash a Pandora’s Box.

Not only could the technology never be uncreated, but a legal precedent would also be set, giving surveillance the upper hand over privacy, privacy advocates say.

“If the order stands, Apple and other technology companies could be ordered to build backdoors – essentially defects – into other devices, rendering them insecure and vulnerable to attack by law enforcement and by others as well,” wrote Director of the Freedom, Security and Technology Project at the Center for Democracy & Technology, Greg Nojeim. “We will fight against this result.”

Yet support for Apple is not universal.

Some question its motives and assert that as Mr. Cook has set himself up as a grand defender of privacy, he had no choice but to fight this battle or lose all credibility.

“As a general matter of strategic communications, following the words 'We have no sympathy for terrorists' with a 'But' generally means you’ve gone badly off message – even if you wedge a few sentences in between,” writes Susan Hennessey and Benjamin Wittes of The Brookings Institution.

“Apple is being mischievous here, and the company’s self-presentation as crusading on behalf of the privacy of its customers is largely self-congratulatory nonsense.”